要获得两个日期之间的精确差并不容易，因为年，月和日的长度是不同的。另外，加法不一定与减法对称，例如4月30日加1月是5月30日，但是5月31日加1月30日还是7月1日吗？与2月29日前后1年相似。
以下内容尝试解决这些问题，因此，如果添加月份超过一个月，则日期将返回到上个月的最后一天。希望评论是足够的，如果不是，请澄清。
该 则DateDiff 函数返回值的年，月，日，等一个数组来获取MM-DD-
HH，只拿到并格式化你想要的任何方式。我提供了一个小的格式化功能，该功能仅打印出非零分量。
// Simple calculation of days between two dates based on time valuefunction getDaysDiff(start, end) { return ((parseStringUTC(end) - parseStringUTC(start))/8.64e7).toFixed(2);}// Expects input in ISO8601 format: yyyy-mm-ddThh:mm:ss.sssZ// Always expects UTCfunction parseStringUTC(s) { s = s.split(/D/); s[6] = s[6]? ('0.'+ s[6]) * 1000 : 0; return new Date(Date.UTC(s[0],--s[1],s[2],s[3]||0,s[4]||0,s[5]||0,s[6]||0));}function dateDiff(d0,d1) { var s = d0.split(/D/); var e = d1.split(/D/); // Calculate initial values for components, // Time component is optional, missing values treated as zero var ms = (e[6]||0) - (s[6]||0); var sec = (e[5]||0) - (s[5]||0); var min = (e[4]||0) - (s[4]||0); var hr = (e[3]||0) - (s[3]||0); var day = e[2] - s[2]; var mon = e[1] - s[1]; var yr = e[0] - s[0]; // Borrowing to resolve -ve values. if (ms < 0) { // ms borrow from sec ms += 1000; --sec; } if (sec < 0) { // sec borrows from min sec += 60; --min; } if (min < 0) { // min borrows from hr min += 60; --hr; } if (hr < 0) { // hr borrows from day hr += 24; --day; } // Day borrows from month, a little complex but not too hard if (day < 0) { var prevMonLen = new Date(e[0], e[1]-1, 0).getDate(); // If the start date is less than the number of days in the previous month, // set days to previous month length + current diff days value // Note that current diff days may have had a day borrowed, so don't use end date - start date // Otherwise, if the start date is equal to or greater than the number of // days in the previous month, just set to end date. That's because adding // 1 month to 30 Jan should be last day in Feb (i.e. 28 or 29), not 2 or 1 March // respectively, which is what happens if adding 1 month to a Date object for 30 Jan. // Similarly, 31 May + 1 month should be 30 June, not 1 July. day = s[2] < prevMonLen? prevMonLen + day : +e[2]; --mon; } if (mon < 0) { // mon borrows from yr mon += 12; --yr; } // If days >= number of days in end month and end date is last day // of month, zero mon and add one to month // If then months = 12, zero and add one to years var endMonLen = new Date(e[0], e[1], 0).getDate(); if (day >= endMonLen && s[2] > e[2] && e[2] == endMonLen) { day = 0; ++mon; if (mon == 12) { mon = 0; ++yr; } } return [yr,mon,day,hr,min,+(sec + '.' + ('00'+ms).slice(-3))];}function formatOutput(v) { var values = ['year','month','day','hour','minute','second'] return v.reduce(function (s, x, i) { s += x? (s.length? ' ' : '') + (i == 5? x.toFixed(3) : x) + ' ' + values[i] + (x==1?'':'s'):''; return s; }, '');}// Tests, focus on Februaryvar dates = [ ['2016-01-31','2016-03-01'], // 1 month 1 day - 31 Jan + 1 month = 29 Feb ['2016-01-29','2016-03-01'], // 1 month 1 day - 29 Jan + 1 month = 29 Feb ['2016-01-27','2016-03-01'], // 1 month 3 days - 27 Jan + 1 month = 27 Feb ['2016-01-27','2016-03-29'], // 2 months 2 days - 27 Jan + 2 month = 27 Mar ['2016-01-29','2016-03-27'], // 1 month 27 days - 29 Jan + 1 month = 29 Feb ['2015-12-31','2016-01-30'], // 30 days- 31 Dec + 30 days = 30 Jan ['2015-12-27','2016-01-30'], // 1 month 3 days - 27 Dec + 1 month = 27 Jan ['2016-02-29','2017-02-28'], // 1 year could also be 11 months 30 days // since 29 Feb + 11 months = 28 Feb, but 28 Feb is last day of month // so roll over to full year // Both work, but 1 year is more logical ['1957-12-04','2016-02-20'], // 58 years 2 months 16 days ['2000-02-29','2016-02-28'], // 15 years 11 months 30 days // Not full year as Feb 2016 has 29 days ['2000-02-28','2016-02-28'], // 16 years ['2000-02-28','2016-02-29'], // 16 years 1 day ['2016-02-28T23:52:19.212Z','2016-12-02T01:48:57.102Z'] // 9 months 3 days 1 hour 56 minutes 37.899 seconds];var arr = [];dates.forEach(function(a) { arr.push(a[0] + ' to ' + a[1] + '<br>' + formatOutput(dateDiff(a[0], a[1])));});document.write(arr.join('<br>')); table { border-collapse:collapse; border-left: 1px solid #bbbbbb; border-top: 1px solid #bbbbbb; } input { width: 12em; } input.bigGuy { width: 32em; } td { border-right: 1px solid #bbbbbb; border-bottom: 1px solid #bbbbbb; } td:nth-child(1) { text-align: right; }<form onsubmit="this.doCalc.onclick(); return false;"> <table> <tr> <td width="250"><label for="startDate">Start date (yyyy-mm-dd)</label> <td><input name="startDate" id="startDate" value="2012-08-09T22:15:03.22" size="25"> <tr> <td><label for="endDate">End date (yyyy-mm-dd)</label> <td><input name="endDate" id="endDate" value="2013-08-13T12:10:03.22" size="25"> <tr> <td><label for="dateDifference">Date difference: </label> <td><input name="dateDifference" readonly > <tr> <td><label for="daysDifference">Days difference: </label> <td><input name="daysDifference" readonly> <tr> <td> <input type="button" value="Calc date difference" name="doCalc2" onclick=" this.form.dateDifference.value = formatOutput(dateDiff(this.form.startDate.value, this.form.endDate.value)); this.form.daysDifference.value = getDaysDiff(this.form.startDate.value, this.form.endDate.value) + ' days'; "> <td><input type="reset"> </table></form>注意事项：
- 5月31日至6月30日为1个月。7月1日是没有意义的。
- 在a年中，1月31日至2月29日为1个月，至2016年2月28日为28天。
- 1月31日至2月28日不是a年，则为1个月。
- 2016年2月29日至2017年2月28日为1年，因为2月28日是该月的最后一天
- 2016年2月29日至2020年2月28日是3年11个月零30天，因为2月28日不是2020年每月的最后一天。
- 无需使用Date对象就可以完全实现此解决方案，为了方便起见，我只是使用它来获取一个月中的日子，但是不使用Date的替代方法大约需要4行代码。
